Genetic and cellular mechanisms of the formation of esophageal atresia and tracheoesophageal fistula.

Foregut separation involves dynamic changes in the activities of signaling pathways and transcription factors. Recent mouse genetic studies demonstrate that some of these pathways interact with each other to form a complex network, leading to a unique dorsal-ventral patterning in the early foregut. In this review, it is discussed how this unique dorsal-ventral patterning is set prior to the foregut separation and how disruption of this patterning affects the separation process. Roles of downstream targets of these pathways in regulating separation at cellular and molecular levels would be discussed further. Understanding the mechanism of normal separation process will provide insights into the pathobiology of a relatively common birth defect, esophageal atresia with/without tracheoesophageal fistula.

Effect of FK506 in reducing scar formation by inducing fibroblast apoptosis after sciatic nerve injury in rats.

We previously demonstrated that FK506, a generally applied immunosuppressant in organ transplantation, could promote peripheral nerve regeneration through reducing scar formation. However, little is known about how FK506 reduces scar formation. Herein we investigated the influence of FK506 on fibroblast proliferation and its correlation with scar formation after sciatic nerve injury in rats, and further explored the effect of FK506 on fibroblast proliferation and apoptosis in vitro. Masson staining and immunohistochemistry revealed that scar area and fibroblast number in the nerve anastomosis of sciatic nerve-injured rats were significantly reduced after FK506 administration. The scar area had a significant positive correlation with the fibroblast number, as detected by linear correlation analysis. CCK-8 assay and flow cytometry indicated that FK506 also inhibited proliferation and induced apoptosis of fibroblasts in vitro. It was primarily phosphorylation of JNK and ERK that were activated during the apoptosis of fibroblast. Pretreatment of cells with JNK inhibitor, SP600125, or ERK inhibitor, PD98059, could inhibit FK506-induced fibroblast apoptosis, respectively. Moreover, simultaneous application of both inhibitors had additive roles in cell protection from apoptosis. These results suggest that FK506-induced fibroblast apoptosis contributes to the suppression of fibroblast proliferation and then results in the reduction of scar formation in sciatic nerve-injured rat, and that JNK and ERK are involved in FK506-induced fibroblast apoptosis.

Epithelial stem/progenitor cells in lung postnatal growth, maintenance, and repair.

The adult lung consists of a trachea leading into a system of branched airways ending in millions of alveolar sacs. It contains many different epithelial cell types arranged in precise patterns along the proximodistal axis. Each region of the lung has the capacity to repair through the proliferation of different epithelial cell types. However, the precise identity of the cells mediating repair is not fully resolved. To address this problem, we are using genetic lineage-labeling techniques in the mouse. The tools we have made will also be useful for understanding how progenitor cell behavior is regulated under normal and pathological conditions.

Unusual persistence in healthy volunteers and ill patients of hyperimmune immunoglobulin directed against multiple Pseudomonas O-chain and Klebsiella serotypes after intravenous infusion.

Persistence of intravenous (i.v.) hyperimmune immunoglobulin (100 mg/kg) directed against clinically predominant serotypes of Pseudomonas and Klebsiella in ill, febrile patients was compared to healthy volunteers to determine if ill patients have a decreased Ig half-life resulting in an increased immunoglobulin requirement. Type-specific antibodies were measured by ELISA for 83 days in eight healthy volunteers and for 35 days in eight ill patients with surgical complications or hematologic malignancy. Mean values and fold rises of antibody concentrations for the two groups were above preinfusion values at 35 days. The antibody fold rises in patients and in healthy volunteers were similar. Type-specific antibody levels in some patients increased after illness coincident with elevation of total immunoglobulins. We conclude that the duration of potentially therapeutic levels of infused type-specific hyperimmune immunoglobulin may persist for a longer period of time than what has been measured for total immunoglobulin. While the mechanism of this persistence remains to be characterized, the possibility of type-specific antibody synthesis induced by immunoglobulin administration must be considered.

Safety and immunogenicity of two Haemophilus influenzae type b polysaccharide-tetanus toxoid conjugate vaccines (PRP-T) given with diphtheria-tetanus-pertussis vaccine to young Papua New Guinean children.

BACKGROUND: In view of high mortality and morbidity from Haemophilus influenzae type b (Hib) in young Papua New Guinean children, the incorporation of a Hib conjugate vaccine into a nationwide immunization program would be of major public health benefit. METHODS: We evaluated the safety and immunogenicity of a lyophilized and a liquid form of Hib polysaccharide-tetanus toxoid conjugate vaccines (PRP-T) given in the same syringe as diphtheria-tetanus-pertussis (DTP) vaccine to children in Goroka, Eastern Highlands Province. In Part 1 of the study 209 children were randomized to receive at ages 1, 2 and 3 months either DTP alone or a liquid formulation of DTP/PRP-T or lyophilized PRP-T dissolved in DTP suspension. A further 75 children were given the liquid DTP/PRP-T formulation at ages 2, 3 and 4 months (Part 2). 54 children aged 15-18 months were given a booster of the same preparation of PRP-T/DTP as they had received during Part 1. Blood for antibody assays was collected at enrolment, before (Part 1 only) and one month after the third dose, then just before and 3 weeks after the booster dose. RESULTS: Follow-up to age of 12 months showed that PRP-T was safe with no evidence of impaired response to individual vaccine components when combined with DTP. Geometric mean titres (GMTs) of anti-PRP antibody before vaccination (n = 64, mean age 41 days), after 2 doses (mean age 99 days) and after 3 doses (mean age 132 days) of the lyophilized formulation were 0.21, 1.48 and 5.04 microg/ml, respectively, with 58% and 89% having anti-PRP antibody titres > or = 1.0 microg/ml after 2 and 3 doses, respectively. Anti-PRP antibody responses to the liquid Hib vaccine formulation were lower (GMT post-dose 3 = 0.48 microg/ml) than to the lyophilized formulation, but better responses were elicited from older children (Part 2; GMT post-dose 3 = 0.78 microg/ml, with 79% > or = 0.15 microg/ml). Both PRP-T preparations elicited excellent booster responses suggesting that children are likely to be protected if exposed to Hib infection. CONCLUSIONS: Lyophilized PRP-T given together with DTP is safe and immunogenic when given to young infants. The liquid DTP/PRP-T formulation showed a lower immunogenicity than in earlier studies with this vaccine, which might have been due to exposure to low temperature during shipment or the younger age at immunization.

Local and systemic immune responses to combined vibrio cholerae CVD103-HgR and salmonella typhi ty21a live oral vaccines after primary immunization and reimmunization.

The local and systemic antibody responses elicited following concomitant primary immunization and reimmunization with the live oral attenuated Vibrio cholerae CVD103-HgR and Salmonella typhi Ty21a vaccine strains were determined in healthy adult volunteers. A more pronounced serum vibriocidal antibody response was generated after primary immunization compared to reimmunization 2.5 or 3.5 yr later. The seroconversion rate (> or =4-fold rise over baseline) was 81% subsequent to primary immunization versus 57% (p=0.018) and 65% (p=0.639) upon reimmunization at 2.5 and 3.5 yr, respectively. A similar trend was observed for serum anti-S. typhi lipopolysaccharide (LPS) antibodies. After primary immunization, 48% of subjects manifested a significant rise in coproantibody levels to V. cholerae LPS while 60% did so for cholera toxin (CT). Upon reimmunization, the response rate for LPS ranged from 38% at 2.5 yr to 56% at 3.5 yr (p>0.05), while that for CT varied from 31% (p=0. 007) to 50% (p=0.541) at 2.5 and 3.5 yr, respectively. The anti-S. typhi IgA coproantibody response rate was 70% subsequent to primary immunization versus 47% at 2.5 yr (p=0.021) and 63% at 3.5 yr (p=0. 77).

Elevated levels of maternal anti-tetanus toxin antibodies do not suppress the immune response to a Haemophilus influenzae type b polyribosylphosphate-tetanus toxoid conjugate vaccine.

Reported are the effects of elevated levels of anti-tetanus antibodies on the safety and immune response to a Haemophilus influenzae type b polyribosylphosphate (PRP)-tetanus toxoid conjugate (PRP-T) vaccine. A group of Thai infants (n = 177) born to women immunized against tetanus during pregnancy were vaccinated with either a combined diphtheria-tetanus-pertussis (DTP) PRP-T vaccine or DTP and a PRP-conjugate vaccine using Neisseria meningitidis group B outer-membrane proteins as a carrier (PedVax HIB). Although most infants possessed high titres (> 1 IU/ml) of anti-tetanus antibodies, the DTP-PRP-T combined vaccine engendered an excellent antibody response to all vaccine components. In both vaccine groups > 98% of infants attained anti-PRP antibody titres > or = 0.15 microgram/ml. The geometric mean anti-PRP antibody titres were 5.41 micrograms/ml and 2.1 micrograms/ml for infants immunized with three doses of PRP-T versus two doses of PedVax HIB vaccines, respectively (P < 0.005). Similarly, the proportion of infants who achieved titres > or = 1 microgram/ml was higher in the PRP-T group (87.8%) than in the group immunized with PedVax HIB (74.2%) (P = 0.036). A subgroup analysis showed that there was no significant difference in the anti-PRP antibody response for infants exhibiting either < 1 IU of anti-tetanus antibody per millilitre or > or = 1 IU/ml at baseline. These finding indicate that pre-existing anti-carrier antibody does not diminish the immune response to the PRP moiety. All infants possessed protective levels of anti-D and anti-T antibody levels after immunization.

PIP: Reported are the effects of elevated levels of anti-tetanus antibodies on the safety and immune response to Haemophilus influenzae type b polyribosylphosphate (PRP)-tetanus toxoid conjugate (PRP-T) vaccine. A group of Thai infants (n = 177) born to women immunized against tetanus during pregnancy were vaccinated with either a combined diptheria-tetanus-pertussis (DTP) PRP-T vaccine or DTP and a PRP-conjugate vaccine using Neisseria meningitidis group B outer-membrane proteins as a carrier (PedVax HIB). Although most infants possessed high titers (1 IU/ml) of anti-tetanus antibodies, the DTP-PRP-T combined vaccine engendered an excellent antibody response to all vaccine components. In both vaccine groups, 98% of infants attained anti-PRP antibody titers of 0.15 mcg/ml or higher. The geometric mean anti-PRP antibody titers were 5.41 mcg/ml and 2.1 mcg/ml for infants immunized with 3 doses of PRP-T vs. 2 doses of PedVax HIB vaccines, respectively (P 0.005). Similarly, the proportion of infants who achieved titers of 1 mcg/ml or higher was greater in the PRP-T group (87.8%) than in the group immunized with PedVax HIB (74.2%) (P = 0.036). A group analysis showed that there was no significant difference in the anti-PRP antibody response for infants exhibiting either less than 1 IU/ml of anti-tetanus antibody or 1 or more IU/ml at baseline. These findings indicate that pre-existing anti-carrier antibody does not diminish the immune response to the PRP moiety. All infants possessed protective levels of anti-D and anti-T levels after immunization.

Does bowel preparation improve the quality of abdominal gallium scintigraphy?

Physiological accumulation of gallium in the intestine is a major weakness of gallium scintigraphy in evaluating the abdomen. In this study, we used two different cathartics to evaluate the efficacy of bowel cleansing in improving the quality of abdominal gallium imaging. One hundred and fifty patients underwent gallium scintigraphy and were randomly divided into three groups. Group A received no bowel preparation, Group B received 30 ml of castor oil the night before imaging, and Group C received bisacodyl the night before imaging. Gallium activity in the intestine was rated on a three-point scale from 0 to II based on the anterior view of a delayed 48-h gallium image. Our data showed that the incidence of gallium accumulation in the small intestine was low. On the contrary, there was high prevalence of gallium activity in the colon. Forty-eight percent of Group A patients had obvious gallium activity in the colon. The percentage decreased significantly to 28% and 22% in Groups B and C, respectively. No significant difference was noted between Group B and Group C. In conclusion, our data suggest that the application of either castor oil or bisacodyl significantly improves the quality of 48-h abdominal gallium scintigraphy. There were no significant differences in the efficacy of bowel cleansing on gallium activity between these two laxatives.

Immunotherapy of sepsis: flawed concept or faulty implementation?

Gram-negative bacillary sepsis is a leading cause of death among patients hospitalized in intensive care units. While initial clinical studies with the passive administration of anti-endotoxin core-glycolipid (CGL) antibodies for the treatment and prophylaxis of sepsis showed promising results, subsequent studies failed to show a consistent benefit. There appears to be a good correlation between anti-CGL antibody levels at the onset of sepsis and maintenance of antibody levels during sepsis with outcome. Previous clinical studies may have failed because insufficient amounts of antibody were administered early in the course of sepsis. Unlike the case with anti-CGL antibodies, polyvalent, hyperimmune type-specific antibody preparations may prevent the development of infections; however, these antibodies also must be provided in adequate amounts and in close proximity to infection in order to provide a beneficial effect. These pharmacokinetic requirements may limit the utility of passive immunotherapy for the prophylaxis of sepsis. Active immunization of acutely traumatized patients or of rats subsequently rendered neutropenic with cyclophosphamide induced high antibody levels for extended periods of time. Since trauma and other conditions are associated with a Th(2) response, these conditions may favor antibody formation following active immunization. Active immunization with both anti-CGL and/or polyvalent-specific vaccines for the prophylaxis of sepsis with passive supplementation at the onset of sepsis is an approach that merits further investigation.

Mucosal and systemic immune responses in humans after primary and booster immunizations with orally administered invasive and noninvasive live attenuated bacteria.

The mucosal and systemic immune responses after primary and booster immunizations with two attenuated live oral vaccine strains derived from a noninvasive (Vibrio cholerae) and an invasive (Salmonella typhi) enteric pathogen were comparatively evaluated. Vaccination with S. typhi Ty21a elicited antibody-secreting cell (ASC) responses specific for S. typhi O9, 12 lipopolysaccharide (LPS), as well as significant increases in levels of immunoglobulin G (IgG) and IgA antibodies to the same antigen in serum. A strong systemic CD4(+) T-helper type 1 cell-mediated immune (CMI) response was also induced. In contrast to results with Ty21a, no evidence of a CMI response was obtained after primary immunization with V. cholerae CVD 103-HgR in spite of the good immunogenicity of the vaccine. Volunteers who received a single dose of CVD 103-HgR primarily developed an IgM ASC response against whole vaccine cells and purified V. cholerae Inaba LPS, and seroconversion of serum vibriocidal antibodies occurred in four of five subjects. Serum IgG anti-cholera toxin antibody titers were of lower magnitude. For both live vaccines, the volunteers still presented significant local immunity 14 months after primary immunization, as revealed by the elevated baseline antibody titers at the time of the booster immunization and the lower ASC, serum IgG, and vibriocidal antibody responses after the booster immunization. These results suggest that local immunity may interfere with colonization of the gut by both vaccine strains at least up to 14 months after basis immunization. Interestingly, despite a low secondary ASC response, Ty21a was able to boost both humoral (anti-LPS systemic IgG and IgA) and CMI responses. Evidence of a CMI response was also observed for one of three volunteers given a cholera vaccine booster dose. The direct comparison of results with two attenuated live oral vaccine strains in human volunteers clearly showed that the capacity of the vaccine strain to colonize specific body compartments conditions the pattern of vaccine-induced immune responses.

Safety and immunogenicity of combined diphtheria-tetanus-pertussis (whole cell and acellular)-Haemophilus influenzae-b conjugate vaccines administered to Indonesian children.

A randomized double-blind trial was conducted to evaluate the safety and immunogenicity of vaccines comprised of diphtheria (D) and tetanus (T) toxoids combined with either a whole cell (P) or an acellular (aP) pertussis component and Haemophilus influenzae type b polyribosylphosphate (PRP) tetanus toxoid conjugate (PRP-T) in Indonesian infants. Three doses of either DTaP, DTaP-PRP-T, or DTP-PRP-T were administered to 930 infants approximately 2-3 months of age and at 2 month intervals thereafter. A booster dose of either DTP-PRP-T or DTaP-PRP-T was administered at 15-18 months of age. Both local and systemic reactions occurred at a significantly (p < 0.001-0.026) higher rate in the group that received whole cell pertussis vaccine versus groups which were immunized with aP containing vaccines. There was no significant difference (p > 0.05) in the rate of adverse events between groups immunized with DTaP or DTaP PRP T. One month after the third dose of vaccine, 99% of subjects had achieved > or =0.1 IU of anti-D and anti-T antibody per ml of serum. The geometric mean titer (GMT) to D was significantly (p < 0.001) higher in the group immunized with DTaP versus the other two groups whereas the anti-T GMT was significantly (p < 0.006) higher for the group immunized with DTP-PRP-T. Both the anti-pertussis toxin (PT) and anti-filamentous hemagglutinin (FHA) antibody levels were significantly (p < 0.001) higher in recipients of acellular versus whole cell pertussis vaccine. In contrast, the anti-B. pertussis agglutinating antibody response was significantly (p < 0.0001) higher in the group immunized with whole cell pertussis vaccine. The anti-PRP GMTs (microg antibody/ml) at 7 months were 0.096, 3.35 and 6.11 for groups immunized with DTaP, DTaP-PRP-T and DTP-PRP-T, respectively. The GMT for those immunized with DTP-PRP-T was significantly (p < 0.001) higher compared to recipients of DTaP-PRP-T. The percent of children who attained > or =0.15 or > or =1 microg/ml after immunization was 18 and 2% for the DTaP group, 93 and 76% for the DTaP-PRP-T group and 97 and 88% for the DTP-PRP-T group. At the > or =1 microg/ml level the difference between the DTaP-PRP0-T and DTP-PRP-T groups was significant (p < 0.01). Children immunized with either DTaP, DTaP-PRP-T, or DTP-PRP-T were reimmunized with DTaP-PRP-T whereas a portion of children immunized with DTP PRP T where also boosted with this vaccine at 15-18 months of age. There was a vigorous anamnestic response to the D and T components with all children possessing > or =0.1 IU/ml. There was also a substantial increase in anti-PT, anti-FHA and B. pertussis agglutinating antibodies. The poorest anti-PT response was seen among children receiving DTP-PRP-T for both primary and reimmunization while the highest agglutinating antibody response followed receipt of 4 doses of DTP-PRP-T. Greater than 80% of children immunized with either DTP PRP T or DTaP-PRP-T possessed > or =0.15 microg/ml before boosting versus 38% for those vaccinated with DTaP (p < 0.001). Primary immunization with DTP-PRP-T resulted in a significantly (p < 0.05) higher percentage (72%) maintaining > or =1 microg/ml compared to those immunized with DTaP-PRP-T (46%). Prior to reimmunization, the anti-PRP GMT was significantly (p < 0.005) higher for children immunized with 3 doses of DTP-PRP-T versus DTaP-PRP-T. Subsequent to reimmunization, > or =95% of subjects attained > or =1 microg/ml.

Immunogenicity of trivalent subunit versus virosome-formulated influenza vaccines in geriatric patients.

The safety and immunogenicity of a commercial trivalent subunit influenza vaccine and an experimental virosome-formulated influenza vaccine were evaluated among geriatric patients in a double-blind, randomized manner. The virosome vaccine was produced by incorporating hemagglutinin (HA) into the membrane of liposomes composed of phosphatidylcholine. Both vaccines elicited a significant (P < 0.01) rise in the geometric mean anti-HA antibody titer to all three vaccine components 1 month after immunization. However, significantly (P < 0.005) more subjects vaccinated with the virosome preparation mounted a more than fourfold rise to the A/Singapore and A/Beijing strains compared with those who received subunit vaccine. The percentage of patients who attained protective levels (anti-HA titer > or = 40) of anti-A/Beijing antibody was also significantly (P < 0.005) higher in the virosome group. Subjects who possessed non-protective baseline antibody levels to the A/Singapore and A/Beijing strains were more likely (P < 0.005-0.030) to achieve protective levels after immunization with the virosome vaccine than with the subunit vaccine. Of particular clinical significance was the fact that 68.4% of subjects immunized with the virosome vaccine attained protective levels of antibody to all three vaccine components versus 38% for the subunit vaccine (P = 0.010).

Safety and immunogenicity of live oral cholera and typhoid vaccines administered alone or in combination with antimalarial drugs, oral polio vaccine, or yellow fever vaccine.

The effects of concomitant administration of antimalarial drugs, oral polio vaccine, or yellow fever vaccine on the immune response elicited by the Vibrio cholerae CVD103-HgR and Salmonella typhi Ty21a live oral vaccines were investigated. Healthy adults were immunized with CVD103-HgR alone or combined with Ty21a. Subjects were randomized to simultaneously receive mefloquine, chloroquine or proguanil, or oral polio or yellow fever vaccine. The vibriocidal antibody seroconversion rate was significantly reduced (P = .008) only in the group that received chloroquine with the CVD103-HgR. The geometric mean vibriocidal antibody titer was significantly decreased in the groups that received chloroquine (P = .001) or mefloquine (P = .02) compared with titers in groups that received CVD103-HgR alone. However, similar immunosuppressive effects were not observed in the groups immunized with Ty21a and CVD103-HgR. Only the concomitant administration of proguanil effected a significant (P = .013) decline in the anti-S. typhi lipopolysaccharide antibody response. These results indicate that chloroquine and proguanil should not be simultaneously administered with the CVD103-HgR and Ty21a vaccine strains, respectively.

Safety and immunogenicity of a Haemophilus influenzae type B polysaccharide-tetanus toxoid conjugate vaccine combined with diphtheria, tetanus and pertussis vaccines in Thai infants.

A randomized, open, multicenter trial was conducted to determine the safety and immunogenicity of a Haemophilus influenzae type b polysaccharide-tetanus toxoid (PRP-T) conjugate vaccine combined with tetanus, diphtheria and pertussis (DTP) vaccine in 271 Thai infants born to mothers immunized against tetanus during pregnancy. Infants were immunized at approximately 2, 4 and 6 months of age with these vaccines. To determine if elevated levels of anti-tetanus toxin antibodies suppressed the anti-PRP antibody response, a second group of infants were immunized with PRP complexed with outer membrane proteins of Neisseria meningitidis (Pedvax HIB) in one limb at 2 and 4 months of age and DTP vaccine in the other limb at 2, 4 and 6 months of age. A third group of infants received only DTP vaccine at 2, 4 and 6 months of age. The occurrence of both local and systemic adverse reactions were comparable in all 3 groups. The geometric mean anti-tetanus antibody titer was > 1 IU/ml at baseline. Approximately 1 month after the administration of the third dose of vaccine, 98.5%, 99.3% and 9.7% of the children immunized with DTP+Pedvax HIB, DTP-PRP-T or DTP possessed > or = 0.15 microgram of anti-PRP antibody per ml. No child in the DTP group achieved > or = 1 microgram/ml while 74.2% and 89.3% did so after immunization with DTP+Pedvax HIB, or DTP-PRP-T, respectively (p < 0.05). Immune responses to diphtheria, tetanus and pertussis antigens were similar in all vaccine groups. These results demonstrate that elevated tetanus antibody titers do not diminish the anti-PRP antibody response following immunization with a PRP-T conjugate combined with DTP vaccine.

Immunization of cystic fibrosis patients with a Pseudomonas aeruginosa O-polysaccharide-toxin A conjugate vaccine.

Healthy, non-colonized cystic fibrosis (CF) patients (N = 26) were immunized with an octavalent Pseudomonas aeruginosa O-polysaccharide-toxin A conjugate vaccine. Vaccination was well tolerated and induced anti-lipopolysaccharide (LPS) antibodies of a high affinity capable of promoting the opsonophagocytic killing of P. aeruginosa by human peripheral lymphocytes. In contrast, anti-LPS antibodies acquired after natural infection possessed a very low affinity and were non-opsonic. To determine if immunization could prevent or delay infections due to P. aeruginosa, the infection rate among immunized patients was compared retrospectively to age and gender-matched controls. After 6 years of clinical follow-up, 15/20 (75%) of control and 8/23 (35%) of immunized subjects were classified as infected (p = 0.022). The persistence of high-affinity antibodies among immunized patients correlated with a significantly lower rate of infection after 4-6 years of observation. Infection of immunized patients was correlated with a dramatic decline in total antibody titer between year 2 and 3 of follow-up. Smooth, typeable strains of P. aeruginosa predominated among immunized patients. In contrast, rough, nontypeable strains were most frequently isolated from nonimmunized patients. Mucoid P. aeruginosa strains were isolated from 6 nonimmunized patients versus only I immunized subject.

A virosome vaccine antigen delivery system does not stimulate an antiphospholipid antibody response in humans.

A virosome vaccine delivery system comprised of the hemagglutinin of influenza A virus incorporated into unilamellar liposomes consisting of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) or only PC was developed. The anti-PE and anti-PC antibody response was determined for human volunteers immunized with a virosome-formulated vaccine against hepatitis A, or a standard or virosome-formulated influenza vaccine. None of the 100 young adults who received two doses of the hepatitis A vaccine 1 year apart mounted a significant (greater than fourfold) antiphospholipid antibody response. Immunization with a single dose of trivalent influenza vaccine engendered a significant anti-PC and anti-PE antibody response in 1 of 32 elderly nursing home residents who received the virosome-formulated influenza vaccine and in 1 of the 31 residents who received a commercial subunit vaccine. These findings indicate that the virosome system can potentiate the human immune response to vaccine antigens without a concomitant rise in antiphospholipid antibodies.

Modulation of excitatory synaptic transmission by low concentrations of glutamate in cultured rat hippocampal neurons.

1. The effects of low micromolar concentrations of glutamate on fast excitatory synaptic responses were studied in microcultures of postnatal rat hippocampal neurons using whole-cell patch clamp recordings. 2. Glutamate depressed the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor component of excitatory autaptic currents (EACs) with an EC50 of 3.8 microM. 3. Both pre- and postsynaptic effects contributed to the depression of AMPA receptor-mediated EACs. Cyclothiazide and wheatgerm agglutinin, agents which inhibit AMPA receptor desensitization, partially reversed the depression produced by glutamate, as did pertussis toxin, an agent that blocks presynaptic inhibition mediated by metabotropic glutamate receptors. 4. In neurons in which both the AMPA and N-methyl-D-aspartate (NMDA) receptor components of EACs were examined, low concentrations of glutamate depressed the NMDA component of EACs to a greater extent. The EC50 for inhibiting the NMDA component was 1.3 microM. 5. Calcium-dependent desensitization of postsynaptic NMDA receptors contributed to the depression of NMDA receptor-mediated synaptic responses. Both depolarization of postsynaptic neurons to +70 mV to decrease Ca2+ influx via NMDA channels and inclusion of high concentrations of a calcium chelator in recording pipettes decreased the depression of NMDA receptor-mediated EACs. 6. Threo-3-hydroxy-aspartate (THA), an inhibitor of glutamate transport, depressed EACs by about 10% and increased the degree of depression produced by 2.5 microM glutamate, suggesting that glutamate transport in microcultures helps to control ambient glutamate levels. 7. Because the normal extracellular concentration of glutamate is about 1 microM, these results suggest that the ambient glutamate level is an important determinant of synaptic efficacy. Relatively small changes in extracellular glutamate can alter fast excitatory synaptic transmission by both presynaptic and postsynaptic mechanisms.